An exhaust gas purification apparatus of an internal combustion engine includes: a reducing agent passage that connects a tank and an injection valve; a heater that heats up a hydrolysis catalyst that is provided in the reducing agent passage; and a controller comprising at least one processor configured to control a pump so that a reducing agent located further toward a side of the injection valve than the hydrolysis catalyst flows toward a side of the hydrolysis catalyst after completion of injection of a reducing agent in a state where the hydrolysis catalyst is at a temperature lower than the hydrolysis temperature and before start of injection of a reducing agent in a state where the hydrolysis catalyst is at a temperature equal to or higher than the hydrolysis temperature.